Field of the Invention
The present invention relates to sensor systems generally and, more specifically, to sensor systems including a sensor for implantation within a living animal for the detection of an analyte in a medium within the living animal by one or more external transceivers communicating with the sensor. The present invention also relates to improved implantation and antenna orientation of the implanted sensor.
Discussion of the Background
A sensor configured to detect an analyte, such as glucose, may be implanted in the body of a living animal, such as a human. The sensor may detect the analyte with florescent indicator molecules that emit an amount of light when irradiated with excitation light. The sensor may be passive (i.e., powered by an external source) and include an antenna to receive power from an external transceiver. An antenna present in the external transceiver may supply energy to the implanted sensor through inductive power transfer (i.e., electromagnetic transmission). The sensor rectifies the power and transfers it to an integrated circuit, which in turn activates a light source (e.g., a light emitting diode (LED)) and digitizes the appropriate response signals. The sensor then transfers the digitized response signals to the transceiver using the sensor antenna. The sensor antenna and the transceiver antenna also transfer information while inductively coupled. For example, the transceiver antenna may provide commands to the sensor, e.g., to measure an analyte, and the sensor antenna may provide analyte measurement information.
Implantable long term sensors are a recent technology and, currently, no sensor geometries and sensor antenna profiles have been developed to fixate or communicate with external transceivers. The implanted sensor may move in the body, which causes the orientation of the sensor antenna to change, as well. The sensor antenna communicates most efficiently with the transceiver antenna when antennas are parallel to each other. However, if the orientation of the sensor antennas changes due to movement of the implanted sensor, the sensor antenna and the transceiver antenna may no longer be parallel to each other. If the sensor rotates between zero and 90°, the charging by the magnetic field will be reduced. If the sensor rotates a full 90° and the sensor antenna is approximately perpendicular to the transceiver antenna, there would be no charging.
Implantable antenna size needs to be relatively large to support more efficient power and data transfer. However, clinicians and patients want a miniature device for a smaller incision and minimal pain or discomfort. In addition, the device should be flexible or elastic (conformable) to improve comfort and facilitate implantation.
Therefore, an implantable sensor is needed with an improved antenna for more efficient power and data transfer and a reduced size during implantation.